2 10 18 36 54 86
He-Ne-Ar-Kr-Xenon-Radon
Because group 0 elements are relatively stable, the outermost electron number is 8 (helium is 2), so they often exist as elemental gas. Its chemical properties are extremely inactive, and it hardly reacts with other substances except a few compounds such as XeF2. In which helium and neon have no compounds.
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Overview of each element
Component serial number: 2
Element symbol: He
Element Name: Helium
Atomic weight of element: 4.003
Element type: nonmetal
Discovered by: Yang Sen
Year of discovery: 1868
Discovery process: 1868, French Zhan Sen first discovered a new element in the sun, namely helium, from the corona spectrum.
Element Description: It is one of the inert elements. Its element helium, with the molecular formula of He, is a rare gas, colorless, odorless and tasteless. Its solubility in water is the smallest among known gases, and it is also the least dense gas except hydrogen. The density is 0. 17847g/L, and the melting point is -272.2℃(26 atmospheres). Boiling point -268.9℃. It is the most difficult gas to liquefy, and its critical temperature is -267.9℃. The critical pressure is 2.25 atmospheres. When the temperature drops below -270.98℃ after liquefaction, it has the characteristics of small surface tension, strong thermal conductivity and strong viscosity. Liquid helium can be used to obtain a low temperature close to absolute zero (-273. 15℃). The chemical properties are very inactive, so it can neither burn nor support combustion.
Source of elements: Helium is the product of radioactive element splitting, and alpha particles are the nucleus of helium. Industrially, it can be extracted from natural gas with reduced helium by 7%. It can also be prepared by fractional distillation from He-Ne mixed gas in liquid air.
Element use: use it to fill electron tubes, balloons, thermometers and diving suits. It is also used as a protective gas for atomic nuclear reactors and accelerators, smelting and welding.
Auxiliary data of elements: In August 1868, 18, French astronomer Zhan Sen went to India to observe the total solar eclipse and the prominence with a spectroscope. From the red flame on the back of the black moon plate, he saw colored stripes, which are the symbolic heat emitted by the sun. He found a yellow line, which is close to the total D 1 and D2 lines of the sodium spectrum. After the eclipse, he also observed this yellow line in the solar spectrum, called D3 line. 1868101on October 20th, the British astronomer lockyer also found such a yellow line.
After further research, it is realized that this is a new line that does not belong to any known element, but is produced by a new element. This new element is named helium, which comes from the Greek helios (the sun) with the symbol he. This is the first element found in the universe outside the earth. To commemorate this event, a gold commemorative plaque was cast, with the legendary image of Apollo, the sun god, driving a four-horse chariot, and the heads of Zhan Sen and lockyer carved on it, and the following words were written: Analysis of the solar prominence on August 1868+08.
More than 20 years later, Ramsar discovered a mysterious gas while studying yttrium uranium ore. Because he studied the spectrum of this gas, he found that it might be the yellow line D3 discovered by Zhan Sen and lockyer. But because he had no instrument to determine the position of spectral lines in the spectrum, he had to turn to crookes, a physicist in London, who was one of the best spectrologists at that time. Crookes proved that this gas is helium. So helium was also found on the earth.
Component serial number: 10
Element symbol: Ne
Element name: neon
Atomic weight of element: 20. 18
Element type: nonmetal
Discovers: Ramsar, Travis.
Year of discovery: 1898
Discovery process: 1898, when Ramsar and Travis in England evaporated liquid hydrogen, neon was discovered in the first gas spectrum.
Element description: one of the rare gas elements, colorless, odorless and tasteless, with gas density of 0.9092g/L, liquid density of 1.204g/cm3, melting point of -248.67℃, boiling point of -245.9℃, extremely inert in chemical properties and ionization energy of 21.564. Another special property of neon is the volume ratio of gas to liquid. Most cryogenic liquid gases produce 500 to 800 volumes of gas at room temperature, while neon produces more than 1400 volumes of gas. This brings convenience to its storage and transportation. 100 liter of air contains about 1.8 18 ml of neon.
Source of elements: While producing oxygen and nitrogen, the mixed gas of neon and helium can be extracted from the air separation tower, and neon can be obtained by liquid hydrogen condensation or activated carbon silica gel adsorption.
Element uses: It is widely used in high-energy physics research, and neon is filled in the spark chamber to detect the behavior of particles. It is also a good raw material for making neon lights and indicator lights. When mixed with argon, it will produce beautiful blue light, and can also be used to fill mercury lamps and sodium vapor lamps. Liquid neon is also used as a refrigerant.
Auxiliary data of elements: After the discovery of argon and helium, Lamsa studied their properties and determined their atomic weights. Then he considered their positions in the periodic table. Because the properties of helium and argon are not similar to other elements that have been found, he proposed to add a new group of chemical elements to the periodic table of chemical elements, and temporarily let helium and argon become members of this group. According to Mendeleev's hypothesis about the periodic classification of elements, he speculated that the family should also have an element with an atomic weight of 20.
During the period of 1896 ~ 1897, Ramsar, with the help of Travis, tried to heat rare metal minerals by the way he discovered helium to obtain the elements he predicted. They tried many minerals, but found none. Finally, they thought of separating the gas from the air. However, it is very difficult to remove argon from the air, and chemical methods are basically impossible. Only by changing the air into a liquid state first, and then using the different boiling points of its components, can it be turned into gases one by one and separated one by one. It takes a lot of pressure and high temperature to change air into liquid. It was at the end of 19 that Linde, a German, and Hampson, an Englishman, created refrigerators and obtained liquid air. 1On May 24th, 898, Lamsa obtained a small amount of liquid air from Hampson. Ramsar and Travis first separated krypton from liquid air. Then they repeatedly liquefied and volatilized the separated argon to collect volatile components. 1898, 12 in June, they finally found the symbol of neon and ne, which comes from the Greek neos (new).
Component serial number: 18
Element symbol: Ar
Element name: argon
Atomic weight of element: 39.95
Element type: nonmetal
Discoverer: Riley
Year of discovery: 1894
Discovery process: 1894, Rayleigh, England. After removing oxygen and nitrogen in the air, argon gas was found in the spectral analysis of a small amount of gas.
Element Description: Its simple substance is a colorless, odorless and tasteless gas. It is the most abundant rare gas in the air, and 100 liter of air contains about 934 ml. Density1.784g/l, melting point-189.2℃. Boiling point-185.7 degrees. The ionization energy is 15.759 eV. Chemically very inactive, according to the general meaning of the word compound, no compound will be formed. Argon can't burn or help combustion.
Source of elements: Argon-containing fraction can be extracted from air fractionator, made into crude argon by argon tower, and then separated into pure argon by chemical reaction and physical adsorption.
Elemental use: The earliest use of argon was to inflate light bulbs. Welding and cutting metals also use a lot of argon. Used as shielding gas for arc welding stainless steel, magnesium, aluminum and other alloys.
Element auxiliary data:1At the end of the 9th century, the British physicist Lord Rayleigh found that the density of nitrogen produced by air impurity removal is about one thousandth different from that produced by ammonia. He published his findings in the prestigious British magazine Nature at that time, and asked everyone to help him analyze the reasons. Ramsar, a professor of chemistry at University of London, concluded that nitrogen in the air may contain a heavier unknown gas. The two of them did a lot of experiments respectively, and finally found that there was an unknown gas in the air whose density was almost one and a half times that of nitrogen.
1894 On August 3rd, the British Science Association held a meeting in Oxford, and Rayleigh gave a report. According to President Martin's suggestion, this new gas is called argon (Greek means "not working" and "lazy"). Element symbol Ar.
Of course, the argon discovered at that time was actually a mixture of argon and other inert gases. It is precisely because the content of inert gas in the air is absolutely dominant that argon is found to be the representative of inert gas.
The discovery of argon began with a slight difference of one thousandth, which was caused by the difference of the third place to the right of the decimal point. Many discoveries of chemical elements and many scientific and technological inventions all started from this tiny difference.
Component serial number: 36
Element symbol: Kr
Element Name: Krypton
Atomic weight of element: 83.80
Element type: nonmetal
Discovers: Ramsar, Travis.
Year of discovery: 1898
Discovery process: 1898, Lamsa and Travis in Britain discovered krypton when analyzing the residual gas left by evaporation of liquid air by spectrum.
Description: Colorless, odorless and tasteless. The density is 3.736 g/L (gas), 2. 155 g/cm3 (liquid,-156.9℃). Melting point-156.6℃, boiling point-152.30 0.10℃ The first ionization energy is 13.999 eV. The shell of krypton atom is a stable structure filled with electrons. Therefore, its chemical properties are extremely inactive, and it can't burn or support combustion. It has the property of absorbing x-rays.
Element source:100L air contains about 0.114ml krypton, which can be separated from the fractions extracted during oxygen or nitrogen production in a large-scale air liquefaction separation tower.
Application of components: mainly used for filling electric lamps and various electronic devices. It can also be used as a shading material for X-ray work. Its mixture with argon is widely used to fill fluorescent lamps.
Auxiliary data of elements: After the discovery of argon and helium, Lamsa studied their properties and determined their atomic weights. Then he considered their positions in the periodic table. Because the properties of helium and argon are not similar to other elements that have been found, he proposed to add a new group of chemical elements to the periodic table of chemical elements, and temporarily let helium and argon become members of this group. According to Mendeleev's hypothesis about periodic classification of elements, he speculated that there should be other elements with atomic weights of 20,82, 129.
During the period of 1896 ~ 1897, Ramsar, with the help of Travis, tried to heat rare metal minerals by the way he discovered helium to obtain the elements he predicted. They tried many minerals, but found none. Finally, they thought of separating the gas from the air. However, it is very difficult to remove argon from the air, and chemical methods are basically impossible. Only by changing the air into a liquid state first, and then using the different boiling points of its components, can it be turned into gases one by one and separated one by one. It takes a lot of pressure and high temperature to change air into liquid. It was at the end of 19 that Linde, a German, and Hampson, an Englishman, created refrigerators and obtained liquid air. 1On May 24th, 898, Lamsa obtained a small amount of liquid air from Hampson. Ramsar and Travis successfully separated a new gas from liquid air. Lamsa decided to call it Kr, which comes from the Greek word krptos.
Component serial number: 54
Element symbol: Xe
Element Name: Xenon
Atomic weight of the element: 13 1.3.
Element type: nonmetal
Discovers: Ramsar, Travis.
Year of discovery: 1898
Discovery process: 1898, xenon was discovered in Ramsar and Travis, England, when liquid krypton was fractionated.
Description: Colorless, odorless and tasteless. It is an inert gas. The densities are 5.887 0.009 g/L, 3.52 g/cm3 (liquid) and 2.7 g/cm3 (solid). Melting point-11.9℃, boiling point-107. 1.3℃ The ionization energy is 12. 130 eV. It is the only element in non-radioactive inert gas that can form compounds that are stable at room temperature and can absorb X-rays. A series of fluorides such as XeF2, XeF4 and XeF6 can be formed with fluorine at high temperature or under illumination. Xenon can also form weak bond inclusions with water, hydroquinone and phenol.
Source of elements: It is separated from the fraction extracted at the same time of oxygen or nitrogen production in a large-scale air liquefaction separation tower.
Element uses: Because of its extremely high luminous intensity, it is used to fill photocells, flashlights and xenon high-pressure lamps in lighting technology. Xenon high-pressure lamp has high ultraviolet radiation and can be used in medical technology.
Auxiliary data of elements: After the discovery of argon and helium, Lamsa studied their properties and determined their atomic weights. Then he considered their positions in the periodic table. Because the properties of helium and argon are not similar to other elements that have been found, he proposed to add a new group of chemical elements to the periodic table of chemical elements, and temporarily let helium and argon become members of this group. According to Mendeleev's hypothesis about periodic classification of elements, he speculated that there should be other elements with atomic weights of 20,82, 129.
1898, Ramsar discovered krypton and neon successively with the help of Travis. Later, with the help of new air liquefaction equipment, they prepared a lot of krypton and neon, which were liquefied and volatilized many times. In July of the same year 12, an inert gas Xenon (xe) was separated from it, which originated from the Greek xenos.
Component serial number: 86
Element symbol: Rn
Element Name: Radon
Atomic weight of element: [222]
Element type: nonmetal
Discoverer: F.E. Donne
Year of discovery: 1900.
Discovery process: 1900 German F.E.Dorn was discovered in uranium products.
Element description: the first ionization energy is 10.748 eV. Colorless gas. The density is 9.73g/L, the melting point is-765438 0℃, and the boiling point is-665438 0.8℃. It is easily adsorbed on adsorbents such as activated carbon and silica gel, so it can be separated from gas impurities; When heated to about 350℃, it can be desorbed from activated carbon. Soluble in water.
Element source: it is obtained by transforming radioactive elements such as radium and thorium.
Element uses: Radon is radioactive and decays into radioactive polonium and alpha particles, so it can be used for medical treatment. Used for radiotherapy of cancer; Inserting a needle filled with radon gas into diseased tissue can kill cancer cells.
Element auxiliary data: When physicists and chemists study the radioactivity of substances, they find that the air around radioactive substances will also become radioactive.
At the end of 19, scientists found that thorium constantly released a gaseous radioactive substance, which was chemically inert and had a large atomic weight. Because it comes from thorium, it is called thorium emanation and symbolizes them. 19 18 German chemist Schmidt named it thorium emanation according to inert gases such as argon and neon. The symbol of this element is Tn, which is officially recognized as an element. 1900, German physicist Donne also discovered the radioactive emission of laser gas, with the symbol RaEM. 19 18, Schmidt renamed it radon, and the element symbol was defined as Rn. In addition, in 1903, actinide, AcEm；; And inert gas neutrons. Later, it was found that thorium emanation was radon 220, actinide emanation was radon 2 19, and niton was radon 222.
Radon is an inert gas, which is the transmutation product of radioactive uranium, radium and thorium in the earth's crust. Therefore, the rocks containing radioactive elements in the earth's crust always diffuse radon around, making the air and groundwater contain some radon more or less. Before the strong earthquake, the geostress activity intensified, and the radon content not only increased, but also changed abnormally. If the underground aquifer is deformed under the action of geostress, it will accelerate the movement of groundwater, enhance the diffusion of radon and increase the radon content. Therefore, measuring radon content in groundwater can be used as an earthquake precursor.
Because radon is a radioactive element, if you inhale high concentration of radon for a long time, it will cause upper respiratory tract and lung damage, and even cause lung cancer. Radon is one of the carcinogens of 19.
oxygen group element
The oxygen group element is a group ⅵ A element in the periodic table of elements (new regulation of IUPAC: 16 group).
This family contains five elements: oxygen (O), sulfur (S), selenium (Se), tellurium (Te) and polonium (Po), among which polonium is a metal, tellurium is a metalloid, and oxygen, sulfur and selenium are typical nonmetallic elements. Under standard conditions, all elements except oxygen are solid.
When combined with metal elements, oxygen, sulfur, selenium and tellurium are usually in the -2 oxidation state; But when sulfur, selenium and tellurium are in their acid radicals, the highest oxidation state can reach +6.
Some transition metals usually exist in the crust in the form of sulfide minerals, such as FeS2 and ZnS. Simple substances such as oxygen, sulfur and selenium can directly combine with hydrogen to form hydride. For example, when sulfur reacts with hydrogen, hydrogen sulfide is produced.
I. Similarities and differences of atomic structures
1. Similarity of atomic structure. There are six electrons in the outermost layer of (1) atom.
(2) Two electrons are easily obtained in the reaction.
(3) showing oxidation.
2. Differences in atomic structure.
(1) The charge of nuclear power increases in turn.
(2) The number of electron layers increases in turn.
(3) With the increase of atomic radius, the ability to acquire electrons decreases and oxidation decreases.
2. Chemical properties of simple materials
1. Similar
(1) can react with most metals.
(2) Both of them can be combined with hydrogenation to generate gaseous hydride.
(3) Both of them can burn in oxygen.
(4) The corresponding hydrate of oxide is acid.
(5) They are all nonmetallic.
2. Degeneracy (from oxygen->; Tellurium)
The stability of (1) gaseous hydride gradually weakens.
(2) The reducibility of gaseous hydrides increases gradually.
(3) The acidity of gaseous hydride aqueous solution gradually increases.
(4) The acidity of hydrate corresponding to the highest valence oxide gradually weakens.
(5) Non-metallic properties gradually weaken.
Tellurium oxysulfide selenium
Nuclear power cost 8 16 34 52
Colorless gas pale yellow solid gray solid silvery white solid at room temperature
Melting, boiling point → rising in turn.
Valence -2 -2, +4, +6 -2, +4, +6 -2, +4 and +6.
React with H2, explode, heat and raise the temperature.
H2R is stable at 1000℃ and easy to decompose when heated at 300℃.
Highest valence hydrate /H2SO4 H2SO4 H2teo4
carbon group element
Ⅳ A group in the periodic table includes five elements: carbon C, silicon si, germanium ge, tin Sn and lead Pb. The shell configuration of valence electrons is ns2np2, with four valence electrons. Carbon and silicon are nonmetals, tin and lead are metals, and germanium is semimetal. Because of its special structure, its ability to gain electrons is almost equal to its ability to lose electrons. It usually obtains a stable structure by using electrons. When combined with atoms of other elements, it mainly forms compounds with valence of * * *.
Carbon and silicon are widely distributed in nature, and the content of carbon is not much, but they are the elements with the most kinds of compounds on the ground. The content of silicon in the earth's crust is second only to oxygen.
Free carbon exists in the form of diamond and graphite, silicon exists in the form of compounds in silicon dioxide and silicate, germanium and tin mainly exist in the form of oxides (Germanane GeO2, cassiterite SnO2), and lead mainly exists in the form of sulfide. Elemental lead is a metal crystal, and the other four elements are atomic crystals (graphite is a layered crystal, and white tin is a metal crystal). Carbon dioxide in the air, various carbonates in the earth's crust, coal and oil all contain a lot of carbon. Organic substances such as fat, sugar and protein are all carbon-containing compounds. Both carbon and tin have allotropes (diamond, graphite and carbon -60, gray tin and white tin, etc.). ).
With the increase of atomic number, the number of electron layers in this group of elements gradually increases, the attraction of nucleus to outer electrons gradually weakens, nonmetals gradually weaken (the ability to gain electrons weakens), and metallicity gradually strengthens (the ability to lose electrons increases). The chemical properties vary greatly.
1. Carbon can react with concentrated sulfuric acid and nitric acid and be oxidized into carbon dioxide, but it cannot react with hydrochloric acid. Silicon does not react with hydrochloric acid, sulfuric acid and nitric acid, but only with hydrofluoric acid. Germanium does not react with dilute hydrochloric acid and dilute sulfuric acid, but can be oxidized by concentrated H2SO4 and concentrated HNO3. Tin reacts with dilute hydrochloric acid and dilute sulfuric acid to produce compounds with low valence of tin (II). React with concentrated H2SO4 and HNO3 to generate compounds with high valence Sn (Ⅳ). Lead can react with hydrochloric acid, sulfuric acid and nitric acid and be oxidized to Pb2+.
2. The reaction of silicon and tin with alkaline solution such as SiO3-releases hydrogen, indicating that tin is not completely metallic.
3. When heated, they can react with oxygen and be oxidized into CO2, SiO2 and PbO.
4. Sulfur and chlorine generate heat to generate corresponding high valence chlorides and sulfides, and lead generates PbS and PbCl2.
5. Carbon and silicon react with metals to form carbides and silicides, and tin and lead form alloys with metals. It cannot be directly combined with hydrogenation, and its hydride is indirectly prepared.
platinum family element
|[& lt； & lt][& gt； & gt]
In mineral classification, platinum group minerals belong to natural platinum subgroup, including four natural elemental minerals: iridium, rhodium, palladium and platinum. There is a wide range of isomorphic substitution between them, thus forming a series of isomorphic mixed crystals. At the same time, its components often contain isomorphic mixtures of iron, copper, nickel and silver. When its content is high, it constitutes the corresponding species. Platinum group elements are all equiaxed crystals, with few single crystals and occasional cubic or octahedral fine crystals. Generally, it is irregular granular, dendritic, grape-like or massive. The color and stripes are silvery white to steel gray, with metallic luster, opacity, cleavage, serrated fracture and ductility, and are good conductors of electricity and heat. Metals smelted from platinum group minerals include palladium, iridium, platinum, rhodium and gold.
1. palladium: It is mainly smelted from natural palladium. The color is silvery white, the appearance is similar to platinum, and it has metallic luster. The hardness is 4~4.5. The relative density is 12. The melting point is 1555℃. The chemical properties are relatively stable. Because the output is higher than platinum and gold, the value is low, and it is rarely used to make jewelry.
2. Rhodium gold: mainly extracted from natural rhodium, it is a rare precious metal. The color is silvery white, metallic and opaque. Hard 4 ~ 4.5, relative density 12.5. High melting point, 1955℃. Stability of chemical reward. Rhodium gold is mainly used in electroplating industry because of its corrosion resistance and good luster. When electroplating on other metal surfaces, the coating is firm in color, not easy to wear and has good reflective effect.
3. Iridium gold: mainly extracted from natural iridium or iridium ore. The color is silvery white, with strong metallic luster and hardness of 7. The relative density is 22.40, which is brittle, but it can be pressed into foil or drawn into filaments at high temperature, and its melting point is as high as 2454℃. The chemical properties are very stable. It is mainly used for manufacturing scientific instruments, thermocouples, resistance twill, etc. High hardness Fe-Ir and Ir-Pt alloys are often used to make pen tips and platinum jewelry.
4. Platinum: It is made of natural platinum, crude platinum ore and other minerals. Because "platinum" is a combination of "gold" and "white" and its color is silvery white, it is also called "platinum". The color is silvery white, metallic luster, hardness is 4 ~ 4.5, and relative density is 2 1.45. High melting point, 1773℃. It is malleable and can be drawn into extremely thin platinum wire and rolled into extremely thin platinum foil. Chemical properties are extremely stable, insoluble in strong acid and strong seal, and do not oxidize in air. Widely used in jewelry industry and chemical industry, used to manufacture advanced chemical vessels, platinum crucibles and catalysts for accelerating chemical reactions.
Chapter 16 Boron Group
Summary of this chapter
1. Similarity between boron and silicon, oxygenated compounds of borane and boron.
2. Two different aluminum salts of Al2O3.
3. Gallium indium thallium oxide and hydroxide salt Tl(III)
0. overview
Boron group is located in ⅲA group, and its valence electron configuration is ns2np 1.
Boron B exists in the form of borate minerals.
Al-Al exists in the form of Al-O bond, and bauxite (Al2O3) is the most extensive mineral, ranking third.
Gallium and gallium coexist with minerals such as zinc, iron, aluminum and chromium.
Indium and sphalerite formation
Thallium Tl and sphalerite formation
Gallium, indium and thallium are rare elements, and there is no separate deposit.
1. boron
1. yellow-brown solid, high hardness, high boiling point, atomic crystal, structural unit B 12 icosahedron.
1. Preparation: reduce B2O3 with magnesium or aluminum.
B2O3+3Mg === 3MgO+2B+2b (high temperature)
Reduction of boron tribromide with H2;
2BBR3+3H2 = = 2B+6HBR (tungsten wire, high temperature)
2. Reaction of Boron
No activity at room temperature, but active at high temperature.
4B + 3O2 === 2B2O3
2B + 3Cl2 === 2BCl3
2B+N2 = = = 20 billion
Reacts with oxidizing acids and is more active than silicon.
B+3HNO3 (concentrated = = = H3BO3+3NO2
React with strong base
2B+2NaOH (concentrated)+H2O = = 2nabo2+3H2 (gas) (sodium metaborate)
Diborane
Although there are not many kinds of hydrocarbons, borohydride is far more than silane, and its structure is more complicated than alkane and silane.
structure
The simplest borane with molecular formula B2H6 has the following chemical bonds:
A σ bond (sp3-s) is formed between H and B on the terminal group. The four terminal H's and two B's form a molecular plane, and the middle two H's are not in the molecular plane. Their connecting lines are perpendicular to the molecular plane, and when they go up and down, the upper H forms a bond.
* * * 44 valence electrons.
Preparation of diborane
Proton replacement method:
Equivalent to the reaction of Mg2Si and hydrochloric acid to prepare SiH4.
Restore method:
4 bcl 3+lia LH 4 = = = 2 B2 h6+3 LiCl+3 ALCL 3
Properties of diborane
1 stability
B2H6 === 2B +3 H2
B H 6 should be stored below 100℃, and its stability is not as good as silane.
2 reducibility
B2h6+3o2 = = B2O3+H2O spontaneous combustion
It is a high-energy fuel, but it is extremely toxic and difficult to store.
3 degree hydrolysis
B2h6+6H2O = = 2b (OH) 3+6H2 (gas)
4 Lewis acid reaction, electron-deficient reaction
B2H6+2LiH === 2Li(BH4 (BH4) white solid, rocket propellant.
Oxygen-containing compound of boron
diboron trioxide
B2O3, a colorless crystal, is obtained by burning boron or dehydrating boric acid.
B2O3+3H2O = = 2h3bo3 boric anhydride
B2O3 reacts with water vapor to generate volatile metaboric acid;
B2O3 + HH2O === 2HBO2
B2O3 and many metal oxides will produce boron beads with characteristic colors when they are melted, which can be used for identification.
Chief Operating Officer +B2O3 = = Co (Bo2) 2 dark blue
Boron bead green of Cr2O3 and boron bead blue of CuO.
Boron bead violet of MnO and boron bead green of NiO.
Iron oxide boron bead yellow
2. Boric acid H3BO3
2 weak acidity
Due to the lack of electronic structure:
Adding glycerol (glycerol) to H3BO3 can enhance the acidity, because the mechanism of showing acidity has changed:
H3BO3 may be alkaline when it meets stronger acids:
B (OH) 3+H3PO4 = = BPO4+3H2O (neutralization reaction)
3 Identification reaction of boric acid
When ignited: triethyl borate burns a green flame.
3. Borax
Borax is the main oxyacid salt of boron, which is white and glassy.
Therefore, borax reacts with transition metal oxides, such as Cr2O3, CuO, MnO, NiO and Fe2O3. But the actual boron bead reaction is made of borax.
Hydrolysis of borax
A certain amount of boric acid and borate are generated to form a buffer solution. The pH value of 0.05438+0 borax solution is 9.24.
Similarity between Tetraboron and Silicon
similar
Except that boron is different from silicon oxide and oxyacid, the preparation of boron and silicon is similar to the action of acid and alkali, the preparation and properties of hydride.
Halogen hydrolyzability of boron and silicon is also similar:
SiCl4 + 4H2O === H4SiO4 + 4HCl
BCl3 + 2H2O === HBO2 + 3HCl
3SiF4+4H2O = = H4SiO4+2H2SiF6 fluosilicic acid
4bf3+2h2o = = hbo2+hbf4fluoroboric acid
Diagonal rule
The downward metallic reinforcement, the right nonmetallic reinforcement, and the right nonmetallic reinforcement are similar. The essence is caused by the electric field force of atoms or ions, which is similar and has similar binding force on outer electrons.
Therefore, the properties of lithium magnesium, beryllium aluminum and boron silicon are similar.
2. Aluminum metal
The reaction between aluminum and acid and alkali, reducibility, the acidity and alkalinity of compounds, and the smelting of aluminum have all been talked about in middle schools.
I. Two variants of alumina
γ-Al2O3: It is prepared by dehydration of Al(OH)3, which is soluble in both acid and alkali.
-Al2O3: If -Al2O3 is burned at high temperature, it will become -Al2O3. -Al2O3 is insoluble in neither acid nor alkali. It and KHSO4***, actually equivalent to the melting of K2S2O7, will become soluble.
Dialuminium salt
Dropping Na2CO3 into Al3+ solution to obtain Al(OH)3 precipitate, but not Al2 (CO3) 3;
Adding Na2S can also precipitate Al(OH)3, but Al2S3 can't be obtained.
Anhydrous AlCl3 salt cannot be crystallized from aqueous solution, so anhydrous AlCl3 should be prepared by dry method.
2al+3cl2 = = 2alcl3 or
Al2O3+3cl2+3c = = 2alcl3+3co (gas)
The fluoride of aluminum is ionic crystal, and other halides have strong valence, so the melting point and boiling point are relatively low.
Gas-phase AlCl3 has dimer molecules and coordination bonds, or the center is chlorine bridge bonds, forming three centers and four electrons.
3. Gallium indium thallium
simple substance
1. Physical properties
Ga, In and TL are all silvery soft metals, which are much softer than lead. The melting point of gallium is 29.78℃, while the boiling point is 2403℃, and the liquid temperature range is the largest. Temperature range of mercury in liquid: -38 ~ 356℃.
2. Chemical properties
And react with non-oxidizing acid.
2Ga+3H2SO4 = = Ga2 (SO4) 3+3H2+3H2 (gas) III valence (in the same reaction).
2Tl+H2SO4 === Tl2SO4+H2+H2 (gas) I valence
And oxidizing acids.
Ga+6HNO3 = = GA (NO3) 3+3NO2+3H2O (In also has the same reaction).
Tl+Tl+2HNO3 === TlNO3+NO2+H2O+H2O cannot oxidize TL to Tl(III).
React with alkali
2Ga+2NaOH+2H2O = = 2nagao2+3H2 (gas) amphoteric
Dioxide and hydroxide
* Ga2O3 and Ga(OH)3 are amphoteric acids;
*Ga(OH)3 is soluble in NH3 H2O and Al (OH) 3 is insoluble in NH3 H2O, so the acidity of Ga(OH)3 is stronger than that of Al(OH)3.
* In _ 2O _ 3 and in (OH) _ 3 have almost no bisexual expression. Indium oxide is soluble in acid, but insoluble in alkali.
According to the sequence of ga (oh) 3, in (oh) 3 and TL (oh) 3, it is easier to dehydrate and generate oxides:
2m (OH) 3 = = M2O3+3H2O (In2O3 yellow)
So that Tl(OH)3 hardly exists.
* Tl2O3 is easy to decompose;
Tl2O3 (brown) == Tl2O (black) +O2 (heating)
* Tl2O is soluble in water, and the formed TlOH is also soluble in water;
Tl2O (black)+H2O = = 2tloh (yellow)
* In hydroxide, TlOH is a strong base (not as good as KOH); Ga(OH)3 is the most acidic.
Oxidation of tri-salt Tl(III)
Tl contains salts and compounds of (Ⅲ) and (Ⅰ), while Ga (Ⅰ) and In (Ⅰ) are difficult to form, and Al (Ⅰ) does not exist. MF3 is an ionic compound, and other halides have valence of * * *, and the B.P. is low. Due to the action of inert electron pairs, Tl(III) has strong oxidation.
TlX is similar to AgX, insoluble in water and can be decomposed by light. Tl(I) is similar to K+ and r b+ when it forms salts with anions with small deformability. For example, Tl2SO4 is easily soluble in water and becomes alum.